This invention relates to a drop jet apparatus, and more particularly relates to a nozzle head suitable for an ink-jet printing apparatus in which the volume of the pressure chamber is changed in response to electric signals and ink droplets are jetted according to the volume changes.
In general, a nozzle head of a drop jet apparatus such as an ink-jet printing apparatus comprises a pressure chamber communicating with a liquid reservoir, a nozzle communicating with the pressure chamber for jetting droplets, and an electro-mechanical transducer such as a piezoelectric plate. A part of the pressure chamber is made by a deflective portion or a so-called diaphragm.
One of conventional nozzle heads has a diaphragm made of piezoelectric crystal, and another has a diaphragm on which a piezoelectric plate is adhered at the whole face contacting therewith as shown in FIGS. 2 and 3 of Japanese Laying-open of Patent Application No. 51-35231. In the latter case, evenness of an adhesion layer between the piezoelectric plate and the diaphragm, as well as relative scale and relative position of the piezoelectric plate to the diaphragm influences directly and greatly on the characteristic of drop formation. The nozzle head, therefore, accompanys difficulty in the adhesion work.
In the former case, that is, when the diaphragm proper is made of piezoelectric crystal, it is necessary that the material is not reactant to and stable to a liquid such as an ink and the diaphragm is sealingly adhered to a housing defining the pressure chamber. Such adhering work is not easy, and freedom in the design of the nozzle head is reduced.